1. Field of the Invention
The present invention relates to a method of feeding paper and a corresponding paper cassette for use in a printer, copier machine, facsimile, or other device utilizing paper. The invention is more particularly related to a paper feeding method and cassette which utilizes corner separators and prevents paper jams during a manual feeding operation by deflecting manually fed papers above the corner separators.
2. Discussion of the Background
There are at least two well known methods of feeding paper into image forming devices such as printers, copier machines, and facsimile machines. These two methods are the feed and reverse roller (FRR) method and the corner separator method. The feed and reverse roller feeding mechanism is illustrated in FIGS. 11 and 12 and the corner separator mechanism is illustrated in FIG. 13.
FIGS. 11 and 12 illustrate a paper cassette which utilizes the feed and reverse roller paper feed mechanism. FIG. 11 illustrates automatic feeding from a stack of papers 23, and FIG. 12 illustrates a manual feed operation. In FIG. 11, a stack of papers 23 rests on a paper support 12a which is raised by a lever 24 during an automatic feed operation so that the top sheet of the stack of paper contacts a pick-up roller 25. There is a pivoting cover 13 which pivots at point 17a, should the stack of papers 23 be pushed up and contact the end of the cover 13. There is also another cover 11 which covers the back of the tray. This feed mechanism also includes a feed roller 27, a reverse roller 28 and a paper sensor 29.
During an automatic feeding operation, the pick-up roller 25 feeds one, or possibly more than one sheet towards the rollers 27 and 28. Should there be only one sheet of paper fed to the rollers 27 and 28, the feed roller 27 rotates clockwise and the reverse roller 28 rotates counter-clockwise due to a rotational force from the feed roller 27 transferred via friction between the rollers and sheet of paper, thus feeding the single sheet of paper to the image forming apparatus. However, if two or more sheets of paper are fed between the feed roller 27 and the reverse roller 28, the reverse roller rotates in the clockwise direction due to a motor as does the feed roller 27. This causes the top sheet to be fed into the image forming apparatus whereas the bottom sheet(s) are returned to the paper cassette. A torque limiter connected to the reverse roller 28 allows the roller 28 to rotate counter-clockwise to feed the paper into the image forming apparatus when there is only one sheet and to rotate clockwise by the force of the motor connected thereto when two or more sheets are fed to the nip between the rollers 27 and 28.
FIG. 12 illustrates the operation of the paper cassette in FIG. 11 operating during a manual feed mode. In this case, a sheet of paper is manually fed to the cover 13 beginning at the position 15. When the manual paper feed sensor 29 detects the manually fed sheet of paper, the pick up roller 25 and feed and reverse rollers 27 and 28 feed a single sheet of paper. During this manual feed operation, the lever 24 may be lowered, if desired, so that paper is not improperly taken from the stack of papers 23. During the manual feed operation, the feed and reverse rollers 27 and 28 operate as described with respect to FIG. 11 so that if the user feeds more than one sheet of paper, only one sheet of paper is fed into the image forming apparatus, due to the reverse rotation of the reverse roller 28. This mechanism provides an effective manner of feeding only a single sheet of paper into an image forming apparatus using either an automatic or manual feed mode of operation.
A negative factor of the feed and reverse roller mechanism illustrated in FIGS. 11 and 12 is that the feed and reverse roller mechanism and associated driving and torqued limiter mechanics require added expense. The corner separator method, discussed below, effectively feeds single sheets of paper from a stack of paper within a paper cassette but does not have the added requirements of the feed and reverse roller mechanism.
FIG. 13 illustrates a manner of feeding single sheets of paper using the corner separation method. In FIG. 13, there is illustrated a stack of papers 52 and a corner separator 4. There is a feeding roller 50 which is in pressured contact with the top sheet of paper P of the stack of paper 52. Friction between the roller 50 and top sheet of paper P is high enough so that the top sheet of paper P is pushed forward and as the corner separator 4 holds down the front corners of the page, the top sheet P flexes, as illustrated in FIG. 13. The flexing or bending action causes the paper to come out from underneath the corner separator 4, thus feeding a single sheet of paper. As the coefficient of friction between the top sheet of paper P and the next lowest sheet is not as high as the coefficient of friction between the feeding roller 50 and the top sheet of paper P, the top sheet of paper P slides along the second highest sheet of paper which allows only one sheet of paper from the stack 52 to be removed.
However, while the corner separation method provides an inexpensive and effective manner of removing a single sheet of paper from a stack of paper within a paper cassette, difficulties arise when a manual feed operation is performed on a single sheet of paper which is also fed using feed roller 50. The inventors have found that by manually feeding a single sheet of paper from a tray which uses the corner separation method, the corner separators might catch the front edge of the sheet of paper being manually fed, thus causing a paper jam.